Method for describing a retardation distribution in a microlithographic projection exposure apparatus

Abstract

In a method for describing a retardation distribution of a light bundle emerging from a selected field point, which passes through a birefringent optical element contained in an optical system of a microlithographic projection exposure apparatus, a distribution of retardation vectors is determined so that precisely one direction of a retardation vector is allocated to each directionless orientation of the retardation. The retardation vector distribution is then at least approximately described as a linear superposition of predetermined vector modes with scalar superposition coefficients.

1 .- 45 . (canceled) 
     
     
         46 . An optical system of a microlithographic projection exposure apparatus, comprising:
 a) a first lens which has a rotationally symmetrical birefringence distribution induced by material stresses, with a tangentially extending slow birefringent axis, and   b) a second lens which has a rotationally symmetrical birefringence distribution induced by material stresses, with a radially extending slow birefringent axis, wherein the magnitude of the birefringence respectively increases at least approximately quadratically as the distance from the symmetry axes of the lenses increases.   
     
     
         47 .- 50 . (canceled)